Hey, I'm still replicating!

Checkpoints exist to ensure the genome is accurately replicated each cell division. But yeast cells don't bother to check that replication is actually completed, report Jordi Torres-Rosell, Luis Aragón (MRC Clinical Sciences Centre, London, UK), and colleagues.

The team was not initially looking for a replication completion checkpoint. They were studying the function of a yeast complex called Smc5-Smc6 that had been suggested to promote DNA recombination and repair.

Budding yeast that lack Smc5-Smc6 do not survive more than a few cell cycles, so the team synchronized yeast cells in G1, knocked out the complex, and then observed the yeast over one cell cycle. S phase and mitosis appeared to be normal. In the subsequent interphase, however, the Rad53 DNA damage signal was activated. This damage response, the team discovered,...